Imaging apparatus

ABSTRACT

Provided is an imaging apparatus including an imaging unit having a plurality of pixels, the pixels each having: a conversion element converting incident light into photoelectrons; a floating diffusion layer electrically connected to the conversion element and converting the photoelectrons into a voltage signal; a differential amplifier circuit electrically connected to the floating diffusion layer, including an amplifier transistor to which a potential of the floating diffusion layer is input, and amplifying the potential of the floating diffusion layer; a feedback transistor electrically connected to the amplifier transistor and initializing the differential amplifier circuit; a clamp capacitance connected in series between the floating diffusion layer and the amplifier transistor; and a reset transistor connected in parallel between the floating diffusion layer and the clamp capacitance and initializing the potential of the floating diffusion layer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/636,147, filed Feb. 3, 2020 which is PCT Nationalization ofPCT/JP2018/024329, filed Jun. 27, 2018 and claims priority to JapanesePriority Patent No. 2017-155855 filed Aug. 10, 2017 and the entirecontents of which are incorporated herein by reference.

FIELD

The present disclose relates to an imaging apparatus.

BACKGROUND

Techniques about imaging elements acquiring high-quality images havebeen developed. Examples of a technique that acquires high-qualityimages by adaptively changing conversion efficiency when electriccharges obtained through photoelectric conversion are converted into avoltage signal include a technique described in Patent Literature 1below.

CITATION LIST Patent Literature

Patent Literature 1: JP 2016-92661 A

SUMMARY Technical Problem

In an imaging element described in Patent Literature 1, for example, avoltage signal obtained through photoelectric conversion is input to adifferential amplifier circuit, and the voltage signal is amplified; theamplified voltage signal is converted into a digital signal by ananalog-to-digital converter (an AD converter) provided for each pixel.The voltage signal is obtained by a floating diffusion layeraccumulating electric charges obtained through photoelectric conversionand converting them into a voltage signal.

In the existing configuration in which the AD converter is provided foreach pixel or for each plurality of pixels, and the voltage signalobtained through photoelectric conversion is input to the differentialamplifier circuit and is amplified, the floating diffusion layer isreset when the differential amplifier circuit performs an Auto-zerooperation. In the existing configuration, the reset potential of thefloating diffusion layer inevitably reduces compared with a case of asource follower reading configuration owing to a voltage drop occurringin a transistor included in an output stage of the differentialamplifier circuit. Examples of the voltage drop occurring in thetransistor included in the output stage of the differential amplifiercircuit include a voltage drop of about 0.30 [V] to 0.45 [V].Consequently, the above configuration may reduce the dynamic range ofthe floating diffusion layer.

The present disclosure presents a novel, improved imaging apparatuscapable of preventing a reduction in the dynamic range of the floatingdiffusion layer.

Solution to Problem

According to the present disclosure, an imaging apparatus is providedthat includes an imaging unit having a plurality of pixels, the pixelseach having: a conversion element converting incident light intophotoelectrons; a floating diffusion layer electrically connected to theconversion element and converting the photoelectrons into a voltagesignal; a differential amplifier circuit electrically connected to thefloating diffusion layer, including an amplifier transistor to which apotential of the floating diffusion layer is input, and amplifying thepotential of the floating diffusion layer; a feedback transistorelectrically connected to the amplifier transistor and initializing thedifferential amplifier circuit; a clamp capacitance connected in seriesbetween the floating diffusion layer and the amplifier transistor; andareset transistor connected in parallel between the floating diffusionlayer and the clamp capacitance and initializing the potential of thefloating diffusion layer.

Advantageous Effects of Invention

The present disclosure can prevent a reduction in the dynamic range of afloating diffusion layer.

The above effect is not necessarily limiting; any effect presented inthe present specification or other effects that can be grasped from thepresent specification may be produced together with the above effect orin place of the above effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustrative diagram of an exemplary configuration of animaging apparatus according to a first embodiment.

FIG. 2 is an illustrative diagram of an exemplary configuration of apixel according to the first embodiment.

FIG. 3 is an illustrative diagram of an exemplary operation of the pixelaccording to the first embodiment.

FIG. 4 is an illustrative diagram of another example of theconfiguration of the pixel according to the first embodiment.

FIG. 5 is a schematic illustrative diagram of an exemplary layout of thepixel according to the first embodiment.

FIG. 6 is a schematic illustrative diagram of an exemplary layout of thepixel according to the first embodiment.

FIG. 7A is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7B is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7C is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7D is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7E is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7F is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7G is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7H is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7I is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 7J is an illustrative diagram of an exemplary layout of the pixelaccording to the first embodiment.

FIG. 8 is an illustrative diagram of an exemplary configuration of thepixel according to a second embodiment.

FIG. 9 is an illustrative diagram of another example of theconfiguration of the pixel according to the second embodiment.

FIG. 10 is a schematic illustrative diagram of an exemplary layout ofthe pixel according to the second embodiment.

FIG. 11 is an illustrative diagram of an exemplary configuration of thepixel according to a third embodiment.

FIG. 12 is an illustrative diagram of another example of theconfiguration of the pixel according to the third embodiment.

FIG. 13 is an illustrative diagram of a layout of the pixel P accordingto the third embodiment.

FIG. 14 is an illustrative diagram of an exemplary layout of a pixelarray of an imaging apparatus according to another embodiment.

FIG. 15 is an illustrative diagram of another example of the layout ofthe pixel array of the imaging apparatus according to the otherembodiment.

FIG. 16 is a block diagram of an exemplary schematic configuration of avehicle control system.

FIG. 17 is an illustrative diagram of exemplary installation positionsof an outside-vehicle information detector and imaging units.

Description of Embodiments

The following describes preferred embodiments of the present disclosurein detail with reference to the accompanying drawings. In the presentspecification and drawings, components having substantially the samefunction are denoted by the same symbols, thereby omitting a duplicatedescription.

In the following, “connecting one component and another component toeach other” refers to “the one component and the other component beingelectrically connected to each other without involving any othercomponents” or “the one component and the other component beingelectrically connected to each other via any other components”.

The following describes the following items in order described below.

1. Imaging Apparatus According to Present Embodiment

[1] Outline of Imaging Apparatus According to Present Embodiment

[2] Imaging Apparatus According to First Embodiment

[3] Imaging Apparatus According to Second Embodiment

[4] Imaging Apparatus According to Third Embodiment

[5] Imaging Apparatus According to Another Embodiment

[6] Effects Produced by Imaging Apparatus According to

Present Embodiment

2. Application Examples of Imaging Apparatus According to PresentEmbodiment

(Imaging Apparatus According to Present Embodiment)

[1] Outline of Imaging Apparatus According to Present Embodiment

As described above, in the existing configuration in which an ADconverter is provided for each pixel or for each plurality of pixels,and a voltage signal obtained through photoelectric conversion is inputto a differential amplifier circuit and is amplified, the resetpotential of a floating diffusion layer reduces by an amountcorresponding to a voltage drop occurring in the differential amplifiercircuit, and the dynamic range of the floating diffusion layer mayreduce.

Given these circumstances, the imaging apparatus according to thepresent embodiment has a configuration preventing the voltage dropoccurring in the differential amplifier circuit from having an influenceon the reset potential of the floating diffusion layer to prevent thereduction in the dynamic range of the floating diffusion layer.

More specifically, a pixel of the imaging apparatus according to thepresent embodiment has “a configuration in which a clamp capacitance isconnected in series between an input terminal of the differentialamplifier circuit and the floating diffusion layer, whereas a resettransistor initializing the potential of the floating diffusion layer isconnected in parallel between the floating diffusion layer and the clampcapacitance”. Having the above configuration, the potential of thefloating diffusion layer can be initialized while preventing the voltagedrop occurring in the differential amplifier circuit from having aninfluence on the reset potential of the floating diffusion layer. Havingthe above configuration, the voltage drop occurring in the differentialamplifier circuit is prevented from having an influence on the resetpotential of the floating diffusion layer, thus preventing the reductionin the dynamic range of the floating diffusion layer.

The following describes a configuration of the imaging apparatusaccording to the present embodiment.

[2] Imaging Apparatus According to First Embodiment

The following first describes an imaging apparatus according to a firstembodiment. FIG. 1 is an illustrative diagram of an exemplaryconfiguration of an imaging apparatus 100 according to the firstembodiment.

The imaging apparatus 100 includes an imaging unit 102 having aplurality of pixels P each performing photoelectric conversion and adriver 104 driving the pixel circuit P, for example. The imagingapparatus 100 is driven by power supplied from an internal power supplysuch as a battery or power supplied from an external power supply.

The imaging unit 102 includes a pixel array in which a plurality ofpixels P are arranged in a matrix manner. The pixels P are eachelectrically connected to the driver 104 via signal lines. Although FIG.1 illustrates an example in which each pixel is connected to the driver104 via one signal line for convenience, the driver 104 and each of thepixels P may be connected to each other via a plurality of signal lines.In the pixel P, accumulation of signal electric charges corresponding toincident light made incident, initialization of the pixel P, and thelike are performed by a control signal transmitted from the driver 104via the signal line.

The imaging unit 102 includes one board or a plurality of laminatedboards, for example. When the imaging unit 102 includes the laminatedboards, among the components included in the pixel P, at least aconversion element (described below), a floating diffusion layer(described below), and a reset transistor (described below) are providedon the same board. The following exemplifies a case in which the imagingunit 102 includes two laminated boards.

An exemplary configuration of the pixel P according to the firstembodiment will be described below.

The configuration of the imaging apparatus according to the firstembodiment is not limited to the example illustrated in FIG. 1.

The imaging apparatus according to the first embodiment does notnecessarily include the driver 104, and each of the pixels P may bedriven by a control signal transmitted from an external driver via asignal line, for example.

The imaging apparatus according to the first embodiment may furtherinclude a conversion unit (not illustrated) converting an analog signaloutput from the pixel P included in the imaging unit 102 into a digitalsignal. The conversion unit (not illustrated) has a conversion circuitconverting the analog signal into the digital signal for each pixel P orfor each plurality of pixels P and converts the analog signal outputfrom the pixel P into the digital signal by the conversion circuit.

Examples of the conversion circuit according to the present embodimentinclude an AD converter with the gain of the analog signal to beconverted into the digital signal fixed. Examples of the AD converterinclude any types of AD converters such as a successive approximation ADconverter. The conversion circuit according to the present embodimentmay be able to adjust the gain of the analog signal to be converted intothe digital signal (be able to switch the gain of the analog signal).

The following describes the exemplary configuration of the pixel P ofthe imaging apparatus 100 with the imaging apparatus 100 illustrated inFIG. 1 exemplified.

The following exemplifies a case in which transistors included in thepixel P are each an N-channel or P-channel metal-oxide-semiconductorfield effect transistor (MOSFET). The transistors included in the pixelP are not limited to the MOSFET. The transistors included in the pixel Pmay be any field-effect transistor (FET) such as a bipolar transistor ora thin-film transistor (TFT), for example. The polarity of thetransistors included in the pixel P is not limited to the followingexample and can be changed in accordance with a signal to be applied toa control terminal of each of the transistors.

[2-1] Exemplary Configuration of Pixel P According to First Embodiment

FIG. 2 is an illustrative diagram of an exemplary configuration of thepixel P according to the first embodiment. FIG. 2 illustrates an examplein which the pixel P includes two boards including a first board B1 anda second board B2.

The pixel P according to the first embodiment includes a conversionelement D, a floating diffusion layer Cfd, a differential amplifiercircuit DA, a feedback transistor Tr_(FB), a clamp capacitance Ccl, anda reset transistor Tr_(RST), for example.

A transfer transistor Tr_(TG) transferring electric chargescorresponding to the conversion of incident light by the conversionelement D to the floating diffusion layer Cfd is connected between theconversion element D and the floating diffusion layer Cfd. The transfertransistor Tr_(TG) becomes an on state (a conductive state) by anapplied control signal TG, whereby the electric charges corresponding tothe conversion of the incident light by the conversion element D aretransferred to the floating diffusion layer Cfd. In the following, thetransfer transistor Tr_(TG) may be denoted as “TG”.

An overflow drain transistor Tr_(OFG) transferring electric charges tothe overflow drain OFD is connected between the conversion element D andthe overflow drain OFD discharging electric charges. The overflow draintransistor Tr_(OFG) becomes an on state by an applied control signalOFG, whereby the electric charges corresponding to the conversion of theincident light by the conversion element D are transferred to theoverflow drain OFD. In the following, the overflow drain transistorTr_(OFG) may be denoted as “OFG”. Excessive electric charges from theconversion element D can also be discharged to a power supply terminal(VDD) via the transfer transistor Tr_(TG) and the reset transistorTr_(RST). When the excessive electric charges from the conversionelement D are discharged to the power supply terminal as describedabove, OFG and OFD illustrated in FIG. 2 can be omitted.

The conversion element D converts incident light into photoelectrons.Examples of the conversion element D include any light-receivingelements capable of converting incident light into photoelectrons suchas a photodiode.

The floating diffusion layer Cfd is connected to the conversion elementD and converts the photoelectrons converted by the conversion element Dinto a voltage signal. The floating diffusion layer Cfd plays a role ofaccumulating the electric charges transferred from the conversionelement D and converting the accumulated electric charges into thevoltage signal and outputting it.

The differential amplifier circuit DA is a differential amplifiercircuit with a general configuration including transistors. Thedifferential amplifier circuit DA includes “an amplifier transistorTr_(AMP) that is connected to the floating diffusion layer Cfd and towhich the voltage signal converted by the floating diffusion layer Cfd(the potential of the floating diffusion layer Cfd, hereinafter thesame) is input” and “a reference transistor Tr_(REF) to which areference signal (an exemplary control signal) is input” as transistorsof an input stage to amplify the voltage signal. A control terminal ofthe amplifier transistor Tr_(AMP) is connected to the floating diffusionlayer Cfd via the clamp capacitance Ccl.

Transistors Tr_(OUT1) and Tr_(OUT2) included in the differentialamplifier circuit DA are transistors included in an output stage of thedifferential amplifier circuit. In the following, the amplifiertransistor Tr_(ANT) may be denoted as “AMP”, whereas the referencetransistor Tr_(REF) may be denoted as “REF”.

The feedback transistor Tr_(FB) is connected to the amplifier transistorTr_(AMP) and initializes the differential amplifier circuit DA. Thefeedback transistor Tr_(FB) becomes an on state, whereby the controlterminal and another terminal of the amplifier transistor Tr_(AMP) areconnected to each other, the potential of the control terminal of theamplifier transistor Tr_(AMP) becomes an initialized potential of thedifferential amplifier circuit DA, and the differential amplifiercircuit DA is initialized. In the following, the operation of thedifferential amplifier circuit DA when the feedback transistor Tr_(FB)becomes the on state may be denotes as “an Auto-zero operation”.

The clamp capacitance Ccl is connected in series between the floatingdiffusion layer Cfd and the amplifier transistor Tr_(Amp). Examples ofthe clamp capacitance Ccl include capacitive elements such as inter-wirecapacitances and capacitors. The clamp capacitance Ccl is provided so asto be a capacitance sufficiently larger than a control terminalcapacitance of the amplifier transistor Tr_(AMP) and an inter-wirecapacitance added to the control terminal of the amplifier transistorTr_(AMP).

The reset transistor Tr_(RST) is connected in parallel between thefloating diffusion layer Cfd and the clamp capacitance Ccl andinitializes the potential of the floating diffusion layer Cfd. The resettransistor Tr_(RST) becomes an on state to initialize the potential ofthe floating diffusion layer Cfd.

FIG. 3 is an illustrative diagram of an exemplary operation in the pixelP according to the first embodiment. Various control signals illustratedin FIG. 3 are supplied from the driver 104 (or an external driver), forexample.

The following first describes an operation to initialize the potentialof the floating diffusion layer Cfd and transfer of the electric chargesfrom the conversion element D to the floating diffusion layer Cfd.

As illustrated in FIG. 3, in the pixel P, when the differentialamplifier circuit DA is performing the

Auto-zero operation (when the feedback transistor Tr_(FB) is in the onstate), the reset transistor Tr_(RST) becomes the on state, and thepotential of the floating diffusion layer Cfd is initialized. In thisprocess, the control terminal of the amplifier transistor Tr_(AMP) (theterminal of the amplifier transistor Tr_(AMP) connected to the floatingdiffusion layer Cfd) is fixed to the initialized potential of thedifferential amplifier circuit DA.

After the potential of the floating diffusion layer Cfd is initialized(after the reset transistor Tr_(RST) becomes an off state (anon-conductive state) from the on state), the Auto-zero operation of thedifferential amplifier circuit DA ends in the pixel P.

After the Auto-zero operation of the differential amplifier circuit DAends, the transfer transistor Tr_(TG) becomes the on state, whereby theconversion element D and the floating diffusion layer Cfd are connectedto each other, and the electric charges corresponding to the conversionof the incident light by the conversion element D are transferred to thefloating diffusion layer Cfd.

The following describes an operation when the voltage signal detected bythe floating diffusion layer Cfd is detected.

As illustrated in FIG. 3, after transfer of the electric charges fromthe conversion element D to the floating diffusion layer Cfd isperformed (after the transfer transistor Tr_(TG) becomes an off statefrom the on state), the feedback transistor Tr_(FB) is in an off state,and the control terminal of the amplifier transistor Tr_(AMP) (theterminal of the amplifier transistor Tr_(AMP) connected to the floatingdiffusion layer Cfd) electrically floats. In this process, the voltagesignal obtained by the floating diffusion layer Cfd is applied to thecontrol terminal of the amplifier transistor Tr_(Amp), and the voltagesignal obtained by the floating diffusion layer Cfd is detected in thepixel P.

It is understood that the example of the various kinds of controlsignals to be supplied to the pixel P according to the first embodimentis not limited to the example illustrated in FIG. 3.

The pixel P according to the first embodiment has a configurationillustrated in FIG. 2, for example.

As illustrated in FIG. 2, in the pixel P according to the firstembodiment, the conversion element D, the floating diffusion layer Cfd,part of the differential amplifier circuit DA including the amplifiertransistor Tr_(AMP), the feedback transistor Tr_(FB), the clampcapacitance Ccl, and the reset transistor Tr_(RST) are provided on thefirst board B1 as the same board. As illustrated in FIG. 2, in the pixelP according to the first embodiment, the output stage of thedifferential amplifier circuit DA (the other part of the differentialamplifier circuit DA) is provided on the second board B2. Consequently,the pixel P according to the first embodiment has two inter-boardjunctions J between the first board B1 and the second board B2.

The configuration of the pixel P according to the first embodiment isnot limited to the example illustrated in FIG. 2.

A plurality of pixels P may share the floating diffusion layer Cfd, thedifferential amplifier circuit DA, the feedback transistor Tr_(FB), theclamp capacitance Ccl, and the reset transistor Tr_(RST), for example.

FIG. 4 is an illustrative diagram of another example of theconfiguration of the pixel P according to the first embodiment andillustrates an exemplary configuration of “a case in which two pixels Pshare the floating diffusion layer Cfd, the differential amplifiercircuit DA, the feedback transistor Tr_(FB), the clamp capacitance Ccl,and the reset transistor Tr_(RST)”.

When the imaging unit 102 has the pixel P of the configurationillustrated in FIG. 4, the conductive states of the transfer transistorsTr_(TG) of the respective pixels P sharing the floating diffusion layerCfd and the like are controlled by the control signal TG, whereby theelectric charges corresponding to the conversion of the incident lightby the conversion elements D of the respective pixels P are eachtransferred to the floating diffusion layer Cfd.

Although FIG. 4 illustrates an example in which two pixels P share thefloating diffusion layer Cfd and the like, three or more pixels P mayshare the floating diffusion layer Cfd and the like in the imaging unit102. As an example, the imaging apparatus 100 according to the firstembodiment can have a configuration in which four pixels P share thefloating diffusion layer Cfd and the like or a configuration in whicheight pixels P share the floating diffusion layer Cfd and the like. Evenwhen three or more pixels P share the floating diffusion layer Cfd andthe like, the conductive states of the transfer transistors

Tr_(TG) of the respective pixels P are controlled, whereby the electriccharges corresponding to the conversion of the incident light by theconversion elements D of the respective pixels P can each be transferredto the floating diffusion layer Cfd.

[2-2] Layout of Pixel P According to First Embodiment

The following shows an exemplary layout of the pixel P according to thefirst embodiment.

FIG. 5 and FIG. 6 are each a schematic illustrative diagram of anexemplary layout of the pixel P according to the first embodiment. FIG.5 illustrates a schematic layout when the pixel P has the configurationillustrated in FIG. 4. FIG. 6 illustrates an exemplary pixel array inwhich the pixels P having the layout illustrated in FIG. 5 are arrangedin a matrix manner.

FIG. 7A to FIG. 7J are each an illustrative diagram of an exemplarylayout of the pixel P according to the first embodiment and eachillustrate an exemplary layout when the pixel P has the configurationillustrated in FIG. 4. B illustrated in FIGS. 7A to 7J are each aschematic diagram of the I-I line section each illustrated in Aillustrated in FIGS. 7A to 7J.

As illustrated in FIGS. 7A to 7J, the pixel P according to the firstembodiment can be achieved by various numbers of wire patterns. It isunderstood that the layout of the pixel P according to the firstembodiment is not limited to the examples illustrated in FIGS. 7A to 7J.

[3] Imaging Apparatus According to Second Embodiment

The following describes an imaging apparatus according to a secondembodiment. The imaging apparatus according to the second embodiment hasa configuration (including modifications) basically similar to theimaging apparatus according to the first embodiment described above, inwhich the configuration of the pixel P is different from that of thepixel P of the imaging apparatus according to the first embodimentdescribed above. Given these circumstances, the following omitsdescriptions of points similar to those of the imaging apparatusaccording to the first embodiment described above in the imagingapparatus according to the second embodiment and describes an exemplaryconfiguration of the pixel P according to the second embodiment.

[3-1] Exemplary Configuration of Pixel P According to Second Embodiment

FIG. 8 is an illustrative diagram of an exemplary configuration of thepixel P according to the second embodiment. FIG. 8 illustrates anexample in which the pixel P includes two boards including the firstboard B1 and the second board B2.

The pixel P according to the second embodiment includes the conversionelement D, the floating diffusion layer Cfd, the differential amplifiercircuit DA, the feedback transistor Tr_(FB), the clamp capacitance Ccl,and the reset transistor Tr_(RST), for example.

A difference between the pixel P according to the second embodiment andthe pixel P according to the first embodiment is a component provided ineach of the first board B1 and the second board B2.

More specifically, as illustrated in FIG. 8, in the pixel P according tothe second embodiment, the conversion element D, the floating diffusionlayer Cfd, the clamp capacitance Ccl, and the reset transistor Tr_(RST)are provided on the first board B1 as the same board. As illustrated inFIG. 8, in the pixel P according to the second embodiment, thedifferential amplifier circuit DA and the feedback transistor Tr_(FB)are provided on the second board B2. Consequently, the pixel P accordingto the second embodiment has one inter-board junction J between thefirst board B1 and the second board B2 and can thus reduce the number ofthe inter-board junctions J compared with the first embodiment.

As illustrated in FIG. 8, for example, the differential amplifiercircuit DA is provided on the board different from the first board B1 onwhich the conversion element D and the like are provided, whereby an Siarea in which the differential amplifier circuit DA is provided can beenlarged. Consequently, the dimensions of the transistors included inthe differential amplifier circuit DA can be ensured to be sufficientlylarge without being limited by the size of the pixel P, and reduction ofcharacteristics such as P (pre-charge) phase variations are prevented,whereby the analog circuit characteristics of the differential amplifiercircuit DA can be improved.

The configuration of the pixel P according to the second embodiment isnot limited to the example illustrated in FIG. 8.

Like the first embodiment, a plurality of pixels P may share thefloating diffusion layer Cfd, the differential amplifier circuit DA, thefeedback transistor Tr_(FB), the clamp capacitance Ccl, and the resettransistor Tr_(RST), for example.

FIG. 9 is an illustrative diagram of another example of theconfiguration of the pixel P according to the second embodiment andillustrates an exemplary configuration of “a case in which two pixels Pshare the floating diffusion layer Cfd, the differential amplifiercircuit DA, the feedback transistor Tr_(FB), the clamp capacitance Ccl,and the reset transistor Tr_(RST)”.

When the imaging unit according to the second embodiment has the pixel Pof the configuration illustrated in FIG. 9, the conductive states of thetransfer transistors Tr_(TG) of the respective pixels P sharing thefloating diffusion layer Cfd and the like are controlled like the casein which the imaging unit has the pixel P of the configurationillustrated in FIG. 4, whereby the electric charges corresponding to theconversion of the incident light by the conversion elements D of therespective pixels P are each transferred to the floating diffusion layerCfd.

Although FIG. 9 illustrates an example in which two pixels P share thefloating diffusion layer Cfd and the like, three or more pixels P mayshare the floating diffusion layer Cfd and the like in the imaging unitaccording to the second embodiment like the imaging unit 102 accordingto the first embodiment.

[3-2] Layout of Pixel P According to Second Embodiment

The following describes an exemplary layout of the pixel P according tothe second embodiment.

FIG. 10 is an illustrative diagram of a layout of the pixel P accordingto the second embodiment and illustrates an exemplary layout when thepixel P has the configuration illustrated in FIG. 9. B illustrated inFIG. 10 is a schematic diagram of the I-I line section illustrated in Aillustrated in FIG. 10.

It is understood that the layout of the pixel P according to the secondembodiment is not limited to the example illustrated in FIG. 10.

A pixel array of the imaging apparatus according to the secondembodiment has a configuration in which the pixels P having the layoutillustrated in FIG. 10 are arranged in a matrix manner like FIG. 6, forexample.

[4] Imaging Apparatus According to Third Embodiment

The following describes an imaging apparatus according to a thirdembodiment. The imaging apparatus according to the third embodiment hasa configuration (including modifications) basically similar to theimaging apparatus according to the first embodiment described above, inwhich the configuration of the pixel P is different from that of thepixel P of the imaging apparatus according to the first embodimentdescribed above and that of the pixel P of the imaging apparatusaccording to the second embodiment described above. Given thesecircumstances, the following omits descriptions of points similar tothose of the imaging apparatus according to the first embodimentdescribed above and the imaging apparatus according to the secondembodiment described above in the imaging apparatus according to thethird embodiment and describes an exemplary configuration of the pixel Paccording to the third embodiment.

[4-1] Exemplary Configuration of Pixel P According to Third Embodiment

FIG. 11 is an illustrative diagram of an exemplary configuration of thepixel P according to the third embodiment. FIG. 11 illustrates anexample in which the pixel P includes two boards including the firstboard B1 and the second board B2.

The pixel P according to the third embodiment includes the conversionelement D, the floating diffusion layer Cfd, the differential amplifiercircuit DA, the feedback transistor Tr_(FB), the clamp capacitance Ccl,and the reset transistor Tr_(RST), for example.

A difference between the pixel P according to the third embodiment andthe pixel P according to the first embodiment and the pixel P accordingto the second embodiment is a component provided in each of the firstboard B1 and the second board B2.

More specifically, as illustrated in FIG. 11, in the pixel P accordingto the third embodiment, the conversion element D, the floatingdiffusion layer Cfd, and the reset transistor Tr_(RST) are provided onthe first board B1 as the same board. As illustrated in FIG. 11, in thepixel P according to the third embodiment, the differential amplifiercircuit DA and the feedback transistor Tr_(FB) are provided on thesecond board B2 like the pixel P according to the second embodiment. Asillustrated in FIG. 11, in the pixel P according to the thirdembodiment, the clamp capacitance Ccl is an inter-wire capacitanceformed of a joining metallic wire joining the board B1 and the board B2together (an exemplary inter-wire capacitance of a wire joiningdifferent boards together). Examples of the joining metallic wireinclude metal for connecting pad.

Consequently, the pixel P according to the third embodiment has oneinter-board junction J between the first board B1 and the second boardB2 like the pixel P according to the second embodiment and can thusreduce the number of the inter-board junctions J compared with the firstembodiment.

The pixel P according to the third embodiment can have a large Si areain which the differential amplifier circuit DA is provided like thepixel P according to the second embodiment and can thus improve theanalog circuit characteristics of the differential amplifier circuit DA.

The pixel P according to the third embodiment can form a capacitanceusing metal for connecting pad and can perform inter-board junction withan insulating film alone, for example, and can thus improve connectionyield.

The configuration of the pixel P according to the third embodiment isnot limited to the example illustrated in FIG. 11.

Like the first embodiment, a plurality of pixels P may share thefloating diffusion layer Cfd, the differential amplifier circuit DA, thefeedback transistor Tr_(FB), the clamp capacitance Ccl, and the resettransistor Tr_(RST), for example.

FIG. 12 is an illustrative diagram of another example of theconfiguration of the pixel P according to the third embodiment andillustrates an exemplary configuration of “a case in which two pixels Pshare the floating diffusion layer Cfd, the differential amplifiercircuit DA, the feedback transistor Tr_(FB), the clamp capacitance Ccl,and the reset transistor Tr_(RST)”.

When the imaging unit according to the third embodiment has the pixel Pof the configuration illustrated in FIG. 12, the conductive states ofthe transfer transistors Tr_(TG) of the respective pixels P sharing thefloating diffusion layer Cfd and the like are controlled like the casein which the imaging unit has the pixel P of the configurationillustrated in FIG. 4, whereby the electric charges corresponding to theconversion of the incident light by the conversion elements D of therespective pixels P are each transferred to the floating diffusion layerCfd.

Although FIG. 12 illustrates an example in which two pixels P share thefloating diffusion layer Cfd and the like, three or more pixels P mayshare the floating diffusion layer Cfd and the like in the imaging unitaccording to the third embodiment like the imaging unit 102 according tothe first embodiment.

[4-2] Layout of Pixel P According to Third Embodiment

The following describes an exemplary layout of the pixel P according tothe third embodiment.

FIG. 13 is an illustrative diagram of a layout of the pixel P accordingto the third embodiment and illustrates an exemplary layout when thepixel P has the configuration illustrated in FIG. 12. B illustrated inFIG. 13 is a schematic diagram of the I-I line section illustrated in Aillustrated in FIG. 13.

It is understood that the layout of the pixel P according to the thirdembodiment is not limited to the example illustrated in FIG. 13.

A pixel array of the imaging apparatus according to the third embodimenthas a configuration in which the pixels P having the layout illustratedin FIG. 13 are arranged in a matrix manner like FIG. 6, for example.

[5] Imaging Apparatus According to Another Embodiment

The imaging apparatus according to the present embodiment is not limitedto the imaging apparatuses according to the first embodiment, the secondembodiment, and the third embodiment described above.

The imaging apparatus according to the present embodiment may further beprovided with an electric shield at “a boundary part between the pixel Psharing one floating diffusion layer Cfd and the pixel P sharing anotherfloating diffusion layer Cfd adjacent to the one floating diffusionlayer Cfd” in order to reduce signal interference between the floatingdiffusion layers Cfd in the pixel array, for example. The electricshield is provided by a wire layer, for example.

FIG. 14 is an illustrative diagram of an exemplary layout of a pixelarray of an imaging apparatus according to another embodiment andillustrates an example in which the clamp capacitance Ccl is formedusing wires within the boards.

As illustrated in A in FIG. 14, an electric shield is provided by a wirelayer at “the boundary part between the pixel P sharing one floatingdiffusion layer Cfd and the pixel P sharing another floating diffusionlayer Cfd adjacent to the one floating diffusion layer Cfd”.

The wire included in the electric shield (hereinafter, denoted as “ashield wire”) is arranged so as to surround the entire boundary part ofthe pixel or to surround part of the boundary part, for example. B inFIG. 14 illustrates an exemplary layout of the shield wire according tothe present embodiment. It is understood that the layout of the shieldwire is not limited to the example illustrated in B in FIG. 14.

The wire layer included in the electric shield (hereinafter, denoted as“a shield wire layer”) includes the same metallic wire layer as eachmetallic wire layer included in the wire of the board including thefloating diffusion layer Cfd, for example. The shield wire layer isconnected to a terminal supplying a standard potential VSS.

Although FIG. 14 illustrates an example in which the clamp capacitanceCcl (the inter-wire capacitance illustrated in FIG. 14) is formed usingthe third wire and the fourth wire from the bottom in FIG. 14, theshield wire can be provided like FIG. 14 also in a case in which theclamp capacitance Ccl is formed using other wires.

FIG. 15 is an illustrative diagram of another example of the layout ofthe pixel array of the imaging apparatus of the other embodiment andillustrates an example in which the clamp capacitance Ccl is formedusing the uppermost wires of the respective boards.

The example illustrated in FIG. 15 is an example in which the clampcapacitance Ccl is formed with the uppermost pad layer viewed from thebottom in FIG. 15. A difference between the example illustrated in FIG.15 and the example illustrated in FIG. 14 is the position at which theclamp capacitance Ccl is formed, and the example illustrated in FIG. 15and the example illustrated in FIG. 14 are the same except for thedifference.

As illustrated in FIG. 14 and FIG. 15, in the imaging apparatusaccording to the other embodiment, the electric shield by the shieldwire is provided, whereby the signal interference between the floatingdiffusion layers Cfd in the pixel array is reduced, for example.

[6] Effects Produced by Imaging Apparatus According to PresentEmbodiment

The imaging apparatus according to the present embodiment produceseffects described below, for example. It is understood that the effectsproduced by the imaging apparatus according to the present embodimentare not limited to the examples described below.

When the potential of the floating diffusion layer Cfd is initialized,the reset potential of the floating diffusion layer Cfd can be a VDDpotential, and thus a reduction in the dynamic range of the floatingdiffusion layer Cfd caused by a voltage drop occurring in the transistorTr_(out2) included in the output stage of the differential amplifiercircuit DA does not occur. When various signals such as a P phase signaland a D (data) phase signal are detected (when the voltage signalobtained by the floating diffusion layer Cfd is detected), the feedbacktransistor Tr_(FB) is in the off state, the capacitance of the floatingdiffusion layer Cfd similar to the capacitance of a floating diffusionlayer according to an existing technique is enough, for example, andthus a reduction in conversion efficiency in the floating diffusionlayer Cfd is reduced.

As in the imaging apparatus according to the second embodiment or theimaging apparatus according to the third embodiment, the differentialamplifier circuit DA is provided on a board different from the board onwhich the conversion element D and the like are provided, whereby thecircuit characteristics of the differential amplifier circuit DA areimproved. The differential amplifier circuit DA is provided on the boarddifferent from the board on which the conversion element D and the likeare provided, whereby the number of the inter-board junction J canfurther be reduced.

(Application Examples of Imaging Apparatus According to PresentEmbodiment)

The imaging apparatus has been described as the present embodiment; thepresent embodiment is not limited to the mode. The present embodimentcan be applied to various image sensors such as “image sensors used inany mobile objects such as vehicles, electric vehicles, hybrid electricvehicles, motorcycles, bicycles, personal mobilities, aircraft, drones,ships, robots, artificial satellites, and survey instruments”,“industrial image sensors used in plants, distribution systems, and thelike”, “image sensors used in intelligent transport systems (ITSs)”, and“crime-prevention image sensors”, for example. The present embodimentcan be applied to any apparatuses including image sensors such as themobile objects including image sensors, for example.

The following describes an example when the technique according to thepresent disclosure is applied to a mobile object.

FIG. 16 is a block diagram of a schematic configuration example of avehicle control system as an exemplary mobile object control system towhich the technique according to the present disclosure can be applied.

This vehicle control system 12000 includes a plurality of electroniccontrol units connected to each other via a communication network 12001.In the example illustrated in FIG. 16, the vehicle control system 12000includes a drive system control unit 12010, a body system control unit12020, an outside-vehicle information detection unit 12030, anin-vehicle information detection unit 12040, and an integral controlunit 12050. Illustrated as functional components of the integral controlunit 12050 are a microcomputer 12051, a voice/image output unit 12052,and a vehicle-mounted network interface (I/F) 12053.

The drive system control unit 12010 controls operations of apparatusesrelated to a drive system of a vehicle in accordance with various kindsof computer programs. The drive system control unit 12010 functions as acontrol apparatus of a driving force generation apparatus for generatinga driving force of the vehicle such as an internal combustion engine ora drive motor, a driving force transmission mechanism for transmittingthe driving force to wheels, a steering mechanism adjusting a steeringangle of the vehicle, a braking apparatus for generating a braking forceof the vehicle, or the like, for example.

The body system control unit 12020 controls operations of various kindsof apparatuses installed in a vehicle body in accordance with variouskinds of computer programs. The body system control unit 12020 functionsas a control apparatus of a keyless entry system, a smart key system,power windows, or various kinds of lights such as headlights, rearlights, breaking lights, blinkers, and fog lights, for example. In thiscase, radio waves transmitted from a portable device replacing a key orsignals of various kinds of switches can be input to the body systemcontrol unit 12020. Upon reception of input of these radio waves orsignals, the body system control unit 12020 controls door locks, powerwindows, lights, and the like of the vehicle.

The outside-vehicle information detection unit 12030 detects informationoutside a vehicle having the vehicle control system 12000 installed. Animaging unit 12031 is connected to the outside-vehicle informationdetection unit 12030, for example. The outside-vehicle informationdetection unit 12030 causes the imaging unit 12031 to take imagesoutside the vehicle and receives the taken images. The outside-vehicleinformation detection unit 12030 may perform object detection processingfor humans, vehicles, obstacles, signs, letters on roads, or the like ordistance detection processing based on the received images.

The imaging unit 12031 is a light sensor receiving light and outputtingan electric signal corresponding to the amount of reception of thelight. The imaging unit 12031 can output the electric signal as an imageand can also output it as distance-measuring information. The lightreceived by the imaging unit 12031 may be visible light or nonvisiblelight such as infrared rays.

The in-vehicle information detection unit 12040 detects in-vehicleinformation. A driver's state detector 12041 detecting the state of adriver is connected to the in-vehicle information detection unit 12040,for example. The driver's state detector 12041 includes a camera fortaking images of the driver, for example; the in-vehicle informationdetection unit 12040 may calculate the degree of fatigue or the degreeof concentration of the driver or determine whether the driver is notfalling asleep based on detection information input from the driver'sstate detector 12041.

The microcomputer 12051 can compute a control target value of thedriving force generation apparatus, the steering mechanism, or thebraking apparatus based on the in- or outside-vehicle informationacquired by the outside-vehicle information detection unit 12030 or thein-vehicle information detection unit 12040 and output control commandsto the drive system control unit 12010. The microcomputer 12051 canperform cooperative control aiming at achieving the function of anadvanced driver assistance system (ADAS) including vehicle collisionavoidance or shock absorption, vehicle distance-based following travel,vehicle speed maintaining travel, vehicle collision warning, and vehiclelane deviation warning, for example.

The microcomputer 12051 controls the driving force generation apparatus,the steering mechanism, or the braking apparatus based on informationaround the vehicle acquired by the outside-vehicle information detectionunit 12030 or the in-vehicle information detection unit 12040 and canthereby perform cooperative control aiming at autonomous drivingautonomously traveling without involving driver's operations and thelike.

The microcomputer 12051 can output control commands to the body systemcontrol unit 12020 based on the outside-vehicle information acquired bythe outside-vehicle information detection unit 12030. The microcomputer12051 can perform cooperative control aiming at antiglare includingcontrolling the headlights in accordance with the position of apreceding vehicle or a vehicle in the opposite lane detected by theoutside-vehicle information detection unit 12030 and switching a highbeam to a low beam, for example.

The voice/image output unit 12052 transmits an output signal, which isat least either a voice or an image, to output apparatuses capable ofproviding visual or auditory information to passengers of the vehicle orto the outside of the vehicle. The example in FIG. 16 exemplifies anaudio speaker 12061, a display unit 12062, and an instrument panel 12063as the output apparatuses. The display unit 12062 may include at leastone of an onboard display and a head-up display, for example.

FIG. 17 is a diagram of exemplary installation positions of the imagingunit 12031.

In FIG. 17, a vehicle 12100 has imaging units 12101, 12102, 12103,12104, and 12105 as the imaging unit 12031.

The imaging units 12101, 12102, 12103, 12104, and 12105 are provided atpositions such as a front nose, side mirrors, a rear bumper, a reardoor, and an upper part of a windshield within a cabin of the vehicle12100, for example.

The imaging unit 12101 provided at the front nose and the imaging unit12105 provided at the upper part of the windshield within the cabinmainly acquire images in front of the vehicle 12100. The imaging units12102 and 12103 provided at the side mirrors mainly acquire images atthe sides of the vehicle 12100. The imaging unit 12104 provided at therear bumper or the rear door mainly acquires images behind the vehicle12100. The forward images acquired by the imaging units 12101 and 12105are mainly used for detection of preceding vehicles or pedestrians,obstacles, traffic signals, traffic signs, traffic lanes, or the like.

FIG. 17 illustrates exemplary imaging ranges of the imaging units 12101to 12104. An imaging range 12111 indicates an imaging range of theimaging unit 12101 provided at the front nose, imaging ranges 12112 and12113 indicate imaging ranges of the imaging units 12102 and 12103,respectively, provided at respective side mirrors, and an imaging range12114 indicates an imaging range of the imaging unit 12104 provided atthe rear bumper or the rear door. Pieces of image data taken by theimaging units 12101 to 12104 are superimposed, whereby a bird's-eyeimage viewing the vehicle 12100 from above is obtained, for example.

At least one of the imaging units 12101 to 12104 may have a function ofacquiring distance information. At least one of the imaging units 12101to 12104 may be a stereo camera including a plurality of imagingelements or an imaging element having pixels for phase differencedetection, for example.

The microcomputer 12051 determines a distance to each solid objectwithin the imaging ranges 12111 to 12114 and a temporal change of thisdistance (a relative speed to the vehicle 12100) based on the distanceinformation obtained from the imaging units 12101 to 12104 and canthereby in particular extract a closest solid object on a traveling roadof the vehicle 12100, the solid object traveling at a certain speed(e.g., 0 km/h or more) in substantially the same direction as thevehicle 12100 as a preceding vehicle, for example. Furthermore, themicrocomputer 12051 can set a following distance to be ensured inadvance before the preceding vehicle to perform automatic brakingcontrol (including following abort control), automatic accelerationcontrol (including following start control), or the like. Thus,cooperative control aiming at autonomous driving autonomously travelingwithout involving driver's operations and the like can be performed.

The microcomputer 12051 can extract pieces of solid object data on solidobjects while classifying them into a motorcycle, a normal vehicle, alarge vehicle, a pedestrian, and other solid objects such as a utilitypole based on the distance information obtained from the imaging units12101 to 12104 and use them for automatic obstacle avoidance, forexample. The microcomputer 12051 discriminates obstacles around thevehicle 12100 between obstacles visually recognizable by the driver ofthe vehicle 12100 and obstacles difficult to be visually recognized, forexample. The microcomputer 12051 determines collision risk indicatingthe degree of risk of a collision with each obstacle and, in a situationin which the collision risk is a set value or more and there is apossibility of a collision, outputs a warning to the driver via theaudio speaker 12061 or the display unit 12062 or performs forced brakingor avoidance steering via the drive system control unit 12010, and canthereby perform driving assistance for collision avoidance.

At least one of the imaging units 12101 to 12104 may be an infraredcamera detecting infrared rays. The microcomputer 12051 determineswhether there are any pedestrians in taken images of the imaging units12101 to 12104 and can thereby recognize pedestrians, for example. Suchrecognition of pedestrians is performed by a step of extractingcharacteristic points in the taken images of the imaging units 12101 to12104 as infrared cameras and a step of performing pattern matchingprocessing on a series of characteristic points indicating the contourof an object to determine whether the object is a pedestrian, forexample. When the microcomputer 12051 determines that there are anypedestrians in the taken images of the imaging units 12101 to 12104 torecognize a pedestrian, the voice/image output unit 12052 controls thedisplay unit 12062 to display a rectangular contour for enhancement in asuperimposed manner on the recognized pedestrian. The voice/image outputunit 12052 may control the display unit 12062 to display an icon or thelike indicating the pedestrian at a desired position.

An exemplary vehicle control system when the technique according to thepresent embodiment is applied to a mobile object has been described. Thetechnique according to the present embodiment can be applied to theimaging unit 12031 in the vehicle control system, for example. It isunderstood that the component to which the technique according to thepresent embodiment is applied is not limited to the imaging unit 12031in the vehicle control system.

The preferred embodiments of the present disclosure have been describedwith reference to the accompanying drawings; the technical scope of thepresent disclosure is not limited to such examples. It is obvious thatthose having normal knowledge in the technical field of the presentdisclosure can think of various kinds of modified examples or correctedexamples within the scope of the technical thought described in theclaims, and it is understood that they also naturally belong to thetechnical scope of the present disclosure.

The effects described in the present specification are only illustrativeand exemplary and are not limiting. In other words, the techniqueaccording to the present disclosure can produce other effects obvious tothose skilled in the art from the descriptions of the presentspecification together with the above effects or in place of the aboveeffects.

The following configurations also belong to the technical scope of thepresent disclosure.

-   (1)

An imaging apparatus comprising an imaging unit having

-   -   a plurality of pixels, the pixels each having:        -   a conversion element converting incident light into            photoelectrons;        -   a floating diffusion layer electrically connected to the            conversion element and converting the photoelectrons into a            voltage signal;        -   a differential amplifier circuit electrically connected to            the floating diffusion layer, including an amplifier            transistor to which a potential of the floating diffusion            layer is input, and amplifying the potential of the floating            diffusion layer;        -   a feedback transistor electrically connected to the            amplifier transistor and initializing the differential            amplifier circuit;        -   a clamp capacitance connected in series between the floating            diffusion layer and the amplifier transistor; and        -   a reset transistor connected in parallel between the            floating diffusion layer and the clamp capacitance and            initializing the potential of the floating diffusion layer.

-   (2)

The imaging apparatus according to (1), wherein the pixels share thefloating diffusion layer, the differential amplifier circuit, thefeedback transistor, the clamp capacitance, and the reset transistor.

-   (3)

The imaging apparatus according to (1) or (2), wherein

the imaging unit includes a plurality of laminated boards, and

at least the conversion element, the floating diffusion layer, and thereset transistor are provided on the same board.

-   (4)

The imaging apparatus according to (3), wherein the conversion element,the floating diffusion layer, part of the differential amplifier circuitincluding the amplifier transistor, the feedback transistor, the clampcapacitance, and the reset transistor are provided on the same board.

-   (5)

The imaging apparatus according to (3), wherein the conversion element,the floating diffusion layer, the clamp capacitance, and the resettransistor are provided on the same board.

-   (6)

The imaging apparatus according to (3), wherein

the conversion element, the floating diffusion layer, and the resettransistor are provided on the same board, and

the clamp capacitance is an inter-wire capacitance of a wire joiningdifferent boards together.

-   (7)

The imaging apparatus according to any one of (1) to (6), wherein

when the potential of the floating diffusion layer is initialized, thefeedback transistor is in an on state, and a terminal of the amplifiertransistor electrically connected to the floating diffusion layer isfixed to an initialized potential of the differential amplifier circuit,and

when the voltage signal obtained by the floating diffusion layer isdetected, the feedback transistor is in an off state, and the terminalof the amplifier transistor is electrically floated.

REFERENCE SIGNS LIST

100 Imaging apparatus

102 Imaging unit

104 Driver

Cfd Floating diffusion layer

Ccl Clamp capacitance

D Conversion element

DA Differential amplifier circuit

P Pixel

Tr_(AMP) Amplifier transistor

Tr_(FB) Feedback transistor

Tr_(RST) Reset transistor

1-7. (canceled)
 8. A light detecting device, comprising: a firstsubstrate including: a plurality of pixels including a first pixel thatincludes a first conversion element, and a first part of a differentialamplifier circuit coupled to the first conversion element via a transfertransistor, a floating diffusion and a capacitor; and a second substratelaminated to the first substrate, the second substrate including: asecond part of the differential amplifier circuit coupled to the firstpart of a differential input circuit; wherein the first part of thedifferential amplifier circuit and the second part of the differentialamplifier circuit are electrically connected by a metal bonding, thecapacitor is coupled in series between the floating diffusion and afirst input of the differential amplifier circuit, and a feedbacktransistor is coupled to the first input of the first part of thedifferential amplifier circuit and configured to initialize thedifferential amplifier circuit.
 9. The light detecting device accordingto claim 8, wherein the first substrate and the second substrate areelectrically connected by a connecting pad.
 10. The light detectingdevice according to claim 9, wherein the first conversion element and asecond conversion element of a second pixel of the plurality of pixelsshare the floating diffusion.
 11. The light detecting device accordingto claim 10, wherein the first part of the differential input circuitincludes the first input and a second input, and the second inputreceives a reference signal.
 12. The light detecting device according toclaim 8, further comprising: a reset transistor connected in parallelbetween the floating diffusion and the capacitor and configured toinitialize a potential of the floating diffusion.
 13. The lightdetecting device according to claim 12, wherein the first pixel and asecond pixel of the plurality of pixels share the floating diffusion,the differential amplifier circuit, the feedback transistor, thecapacitor, and the reset transistor.
 14. The light detecting deviceaccording to claim 8, wherein the feedback transistor is located on thesecond substrate.
 15. The light detecting device according to claim 12,wherein the feedback transistor is located on the second substrate, andthe reset transistor is located on the first substrate.
 16. The lightdetecting device according to claim 15, wherein the capacitor is locatedon the first substrate.
 17. The light detecting device according toclaim 8, wherein when a potential of the floating diffusion isinitialized, the feedback transistor is in an on state, and a terminalof the differential amplifier circuit electrically connected to thefloating diffusion is fixed to an initialized potential, and when avoltage signal obtained by the floating diffusion is detected, thefeedback transistor is in an off state, and the terminal of thedifferential amplifier circuit is electrically floated.